Vehicle body tilt control devices are known that improve the ride comfort in a railroad vehicle traversing a track curve. A vehicle body tilt control device tilts the vehicle body by controlling the supply and/or exhaust of air to and from four air springs located between the vehicle body of a vehicle and a pair of bogies.
More specifically, when a vehicle is traversing a track curve, the vehicle body tilt control device supplies air to the air springs located above the outer rail to increase the height of these air springs and exhausts air from the air springs located above the inner rail to reduce the height of these air springs. This tilts the vehicle body toward the interior of the curve.
For example, Patent Document 1 (Japanese Patent No. 5182239) proposes a vehicle body tilt control device including air springs each having a spool-type flow proportional valve, a supply-side block valve (electromagnetic valve), and an exhaust-side block valve (electromagnetic valve). The spool-type flow proportional valve slides its spool and stops it at different positions to control the flow rate for air supplied to and exhausted from the associated air spring. The supply-side block valve is provided in the piping connecting the spool-type flow proportional valve to the air pressure source (i.e. source pressure reservoir) for controlling the supply of air to the spool-type flow proportional valve. The exhaust-side block valve is provided in the piping connecting the spool-type flow proportional valve to an exhaust port to control the exhaust of air from the spool-type flow proportional valve.
Of various abnormalities in supply and exhaust of air to and from air springs by the vehicle body tilt control device described in Patent Document 1, one particularly problematic one is the exhaust-side block valve remaining closed. As discussed above, when a vehicle is traversing a track curve, the vehicle body tilt control device supplies air to the air springs located above the outer rail to increase the height of these air springs to tilt the vehicle body. If the exhaust-side block valve remains closed, air in the air springs located above the outer rail cannot be exhausted therefrom, which means that the height of these air springs cannot return to its original level. As such, after the vehicle has finished traversing the track curve, the vehicle body cannot be returned to its horizontal position.
A method for detecting abnormalities in a vehicle body tilt control device is proposed by Patent Document 2 (Japanese Patent No. 5038615), for example. The method described in Patent Document 2 determines that there is an abnormality when the value of a predetermined equation represented by the heights of four air springs exceeds a predetermined threshold.
While the method described in Patent Document 2 is capable of determining that there is an abnormality in the vehicle body tilt control device, it cannot determine which one of the four air springs has an air supply/exhaust abnormality. As such, the vehicle body tilt control device must switch to the air supply/exhaust control using the differential pressure regulating valve or LV valve typically included in the device to return the vehicle body to its horizontal position. However, these valves typically have low flow rates such that the vehicle body can only return to its original position very slowly. Thus, passengers feel gravity in the left/right direction for a prolonged period of time, which significantly impairs ride comfort. Furthermore, since it cannot be determined which air spring has an air supply/exhaust abnormality, the work in repairs is complicated.